Introduction: The growth of social networks has led to definition of new applications, including informal and tacit trainings (visual, auditory and written) for this tool. The present study aimed to examine the effect of using telegram social network on the effectiveness of nurses' professional trainings.Methods: This study utilized a multi-group pretest-posttest design. Based on the inclusion criteria, 90 nurses were selected from one of the private specialized hospitals in Tehran and randomly divided into three groups of 30. Each group was assigned to one type of training (face-to-face, self-reading and telegram-based). Statistical analysis was performed using descriptive statistics, one-way ANOVA and factor analysis. Results:The mean score of the telegram-based group was 3.7 points higher than that of the self-reading group and 1.66 points higher than that of the face-to-face group. The mean score of the face-to-face group was 2.3 points higher than that of the self-reading group. In addition, the two variables working hours (-0.19) and teaching method (0.33) and the two variables age (0.178) and job experience (-0.08) had a direct and indirect effect respectively on the participants’ scores. The greatest effect was related to the teaching method (0.53) and the smallest effect was related to the job experience.Conclusion: Nursing managers can use mobile social networks to improve the effectiveness of nursing in-service training programs. The results of this study can serve as a useful guide for supervisors.